Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $85.89   10.744%   $95.118   $95.12   $95.10   $95.10  
  Purchase #2 $181.73   9.674%   $199.3106   $199.31   $199.30   $199.30  
  Purchase #3 $56.41   6.665%   $60.1697   $60.17   $60.15   $60.20  
  Purchase #4 $250.36   9.810%   $274.9203   $274.92   $274.90   $274.90  
  Purchase #5 $9.51   11.693%   $10.622   $10.62   $10.60   $10.60  
  Purchase #6 $167.82   9.689%   $184.0801   $184.08   $184.10   $184.10  
  Purchase #7 $135.57   8.695%   $147.3578   $147.36   $147.35   $147.40  
  7 purchase totals = $887.29       $971.5785   $971.58   $971.50   $971.60